/Engine/Source/Runtime/InteractiveToolsFramework/Public/InteractiveToolBuilder.h
PostBuildTool is called by the ToolManager after a new Tool instance has been built. This allows clients to extend a ToolBuilder with additional customization/etc, instead of having to entirely replace the existingBuildTool()a new instance of the Tool, or nullptr on error/failure
virtual void PostBuildTool ( [UInteractiveTool](API\Runtime\InteractiveToolsFramework\UInteractiveTool) * Tool, const [FToolBuilderState](API\Runtime\InteractiveToolsFramework\FToolBuilderState) & SceneState ) const